Aldehydes from acid derivatives

Reductive Methods.—Aldehydes from Acid Derivatives. Acid chlorides are reduced to aldehydes by sodium borohydride in the presence of cadmium(il) 

Matsumura, J. Hayashi, and M. Mizoguchi, Tetrahedron Lett., 1980, 21,1867. 

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Neqifihi. E. Swanson, D.R. Miller, S.R. Tetrahedron Lett., 1988, 29.1631. SECTION 47 ALDEHYDES FROM ACID DERIVATIVES... 

The following scheme summarizes how lithium tri-rcrr-butoxyaluminum hydride and DIBAL-H can be used to synthesize aldehydes from acid derivatives ... 

Of the methods used for converting amides to aldehydes the one utilizing lithium triethoxyaluminohydride is most universal, can be applied to many types of amides and gives highest yields. In this way it parallels other methods for the preparation of aldehydes from acids or their derivatives (p. 148). 

Distinguishing aldehydes and ketones from acid derivatives... 

Apart from acid derivatives, aldehydes and ketones are also versatile reagents. The (5-benz-y]ideneamino)pyrimidine which is formed initially undergoes ring closure on reaction with an oxidizing agent such as iron(III) chloride or iron(III) oxide. ... 

B.vii. Acid Dianions. All of the named reactions discussed in Section 9.4 constitute relatively minor variations of the fundamental condensation reaction of aldehydes, ketones, or acid derivatives with another aldehyde, ketone, or acid derivative. The ability to produce kinetic enolates from acid derivatives has made possible another useful modification of the enolate reaction. Carboxylic acids have an acidic proton that is removed by 1 equivalent of base to first give a carboxylate (see 226). Addition of a second equivalent of a powerful base such as a dialkylamide leads to the dianion (227). Subsequent reaction with an electrophilic species, in this case 1-bromobutane, occurred first at the more nucleophilic a-carbon to give hexanoic acid. 2 The carboxylate is usually generated with n-butyllithium and the enolate with LDA, although 2 equivalents of LDA can be used. As discussed in Chapter 8, treatment of a carboxylic acid with an excess of an organo-... 

Oxidations with phosphatoplumbic acid Aldehydes from ethylene derivatives Oxidative cleavage... 

Disulfides are good soft acceptors. They are reduced to thiols by hydro-selenide ion (90). The utilization of dimethyl disulfide as an indirect oxidant during conversion of aldehyde to acid derivatives via the dithiane synthesis has been reported (91). The alkylation of the lithiodithiane derived from cinnam-aldehyde occurs exclusively at the heterocyclic carbon. This may be indicative of symbiotic stabilization of the transition state and the product. 

Peroxyacetic acid sodium carbonate Aldehydes from ethylene derivatives with rearrangement s. 18,187... 

Apart from the thoroughly studied aqueous Diels-Alder reaction, a limited number of other transformations have been reported to benefit considerably from the use of water. These include the aldol condensation , the benzoin condensation , the Baylis-Hillman reaction (tertiary-amine catalysed coupling of aldehydes with acrylic acid derivatives) and pericyclic reactions like the 1,3-dipolar cycloaddition and the Qaisen rearrangement (see below). These reactions have one thing in common a negative volume of activation. This observation has tempted many authors to propose hydrophobic effects as primary cause of ftie observed rate enhancements. 

Reactions. Heating an aqueous solution of malonic acid above 70°C results in its decomposition to acetic acid and carbon dioxide. Malonic acid is a useful tool for synthesizing a-unsaturated carboxyUc acids because of its abiUty to undergo decarboxylation and condensation with aldehydes or ketones at the methylene group. Cinnamic acids are formed from the reaction of malonic acid and benzaldehyde derivatives (1). If aUphatic aldehydes are used acryhc acids result (2). Similarly this facile decarboxylation combined with the condensation with an activated double bond yields a-substituted acetic acid derivatives. For example, 4-thiazohdine acetic acids (2) are readily prepared from 2,5-dihydro-l,3-thiazoles (3). A further feature of malonic acid is that it does not form an anhydride when heated with phosphorous pentoxide [1314-56-3] but rather carbon suboxide [504-64-3] [0=C=C=0], a toxic gas that reacts with water to reform malonic acid. 

Carbon, hydrogen and possibly oxygen Resin and derivatives Natural drying oils Cellulose derivatives Alkyd resins Epoxy resins (uncured) Phenol-formaldehyde resins Polystyrene Acrylic resins Natural and synthetic rubbers Carbon monoxide Aldehydes (particularly formaldehyde, acrolein and unsaturated aldehydes) Carboxylic acids Phenols Unsaturated hydrocarbons Monomers, e.g. from polystyrene and acrylic resins... 

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